The present invention relates to a waveform equivalent circuit which shapes an isolated signal waveform and, more particularly, to a waveform equivalent circuit which corrects the asymmetry of each signal waveform retrieved from a magnetic recording medium by a magnetic head.
Generally, a magnetic recording apparatus, e.g., a magnetic disk unit, operates to record information in the form of digital data represented by "0"s and "1"s states of magnetism on the magnetic disk. Recently, in order to record a larger amount of information on a magnetic disk, information is recorded with a smaller interval between adjacent magnetic transitions on the magnetic disk. However, when such a record with a smaller transition interval is read out by a magnetic head, the adjoining magnetic states interfere with each other, causing the reproduced adjoining waveforms to shift away from each other. This phenomenon is called "pattern peak shift", and it reduces the amplitude and shifts the peak position of the signal, resulting in the failure of accurate reproduction of signals from the recording medium. On this account, magnetic recording apparatus designed for high density recording need a waveform equivalent circuit which modifies the reproduced waveform so that it has symmetric and acute slopes.
With regard to a technology of removing the pattern peak shift, reference may be made to U.S. Pat. No. 4,000,513 which discloses a technology of controlling a write timing of digital data to prevent the generation of peak shift in a reproduced waveform.